Clay particles have long been used for providing small animals with dry, sanitary, dustless and relatively odorless litter and bedding. For example, U.S. Pat. No. 2,649,759 to Gibbs describes the use of porous calcined clay as a litter for poultry and small animals.
Similarly, swelling clays have long been recognized as one means of facilitating separation and removal of urine-soaked clay particles from an otherwise fresh bed of animal litter. Such clays expand in volume and become tacky when wetted, forming clumps of spent clay which can be individually removed from the bed. U.S. Pat. No. 5,000,115 to Hughes describes a method and a composition of absorbing animal dross using a swellable clay.
The swelling clay, upon contact with water, typically expands to ten or more times its original dry volume. If not completely loaded with animal urine at the time of disposal, the swelling clay will continue to expand when contacted with additional liquids as, for example, within a household plumbing system. During a period of continued swelling, the swelling clay has a propensity for becoming lodged within any recess, nook, or cranny, where it may otherwise have only temporarily come to rest.
This shortcoming of the swelling clay is compounded by a tacky surface texture which often accompanies the swelling of the clay. Further, because the swelling clay is an inorganic material that is not subject to biodegradation, a deposit of the swelling clay once lodged will tend to persist and accumulate more deposits Over a period of time, the household plumbing system in which they are lodged may become blocked.
At least partly to avoid the plumbing blockages associated with the swelling clays, clumping agents have been devised which, when added to a bed containing non-swelling clay particles, cause the particles to clump together into an agglomeration of sufficient size and strength be removed by a sieving spoon. U.S. Pat. No. 4,638,763 to Greenberg describes a litter composition utilizing anhydrous sodium sulfate as a clumping agent. On contact with liquid water, the sodium sulfate presumably dissolves to form an aqueous solution which can be removed from household waste water, if at all, only by sophisticated tertiary water treating equipment. The United States Government currently sets limits on the concentration and amount of sulfates which municipalities may discharge from their treatment facilities. A need exists for a biodegradable clumping agent capable of acting upon particles of non-swelling clay.
U.S. Pat. No. 4,591,581 to Crampton et al. recommends polysaccharides, such as carboxymethyl cellulose, hydroxypropyl cellulose, and soluble gums which hydrate in water, as ingredients intimately admixed with clay fines for increasing the absorbency of a pressure-compacted clay mineral particle suitable for use as cat litter. Polysaccharides are generally biodegradable. However, since these polysaccharide additives must be distributed throughout the pressure compacted clay particles, it is unlikely that the additives would be present in sufficient concentration on the surface of the mineral clay particles to produce clumping when contacted by excreted animal body fluids
U.S. Pat. No. 5,014,650 to Sowle et al. describes animal litter which is a dry blend of a porous, inert solid substrate, such as particulate clay, and a dry, particulate cellulosic ether. U.S. Pat. No. 4,685,420 to Stuart describes a similar animal litter that utilizes dry blends of clay with a particulate water-absorbent polymer. When excreted animal body fluids contact such litter, gelled agglomerates, or clumps, are produced.
While the foregoing type of clumping animal litter avoids the aforementioned shortcomings of the animal litters derived from swelling clays such as sodium bentonite, the animal litter nevertheless is dusty during manufacture, as well as dispensing. In addition, in such animal litter, the dry particulate cellulosic ether or the water-absorbent polymer tend to segregate from the particulate clay during handling and shipping.
What is needed is a relatively dust-free clumping animal litter that can be periodically disposed through a household plumbing system without fouling the system or creating an environmental nuisance. The clumping agent should not be so sensitive as to be triggered by water vapor which is always present in the atmosphere, and should not separate from the particulate clay during handling, yet should respond relatively quickly upon contact with excreted body fluids. A desirable clumping agent forms clumps strong enough for separation and disposal within a few minutes after formation. Ideally, the clumps hold together and remain durable for a period of at least a day or two, rather than weaken or disintegrate over time.
Animals may ingest some of the animal litter while grooming. Therefore, it is important that all of the components of the animal litter be safe for animal consumption. This is especially true for animal litter which will be used by household pets and may occasionally be spilled or tracked about a floor of a home.